At a parking time of an aircraft, operations of boarding and alighting of a crew and passengers, loading and unloading of cargo and baggage, loading of fuel, loading and unloading of goods to be served such as in-flight meals (in an official demand aircraft, equipment for mission and the like), loading of clean water, discharge of dirty water and the like are performed, and therefore, change in the attitude mainly in a pitch direction (movement in a forward inclination direction and a backward inclination direction with the vicinity of the center of gravity of a fuselage as a center) and vertical motion occur.
In general, in the weight and balance design of a fuselage, sufficient consideration is also given so that a fuselage keeps a stable attitude, in consideration of external factors (surface wind, snow coverage, engine slip streams of other aircrafts passing nearby and the like), in addition to the above-described change of the attitude.
Further, in the case where sufficient countermeasures cannot be taken with only consideration in specification design as typified by a cargo plane, the operation procedures are sometimes set so that an aircraft does not have an extremely pitch-up attitude. For example, such operation procedures are applied that after a cargo compartment at a fuselage front side is filled, cargo is loaded into a cargo compartment at a fuselage rear side, or while a fuel loading amount into a fuel tank located inside a main wing does not reach a predetermined amount, loading into a cargo compartment at a fuselage rear side is not started.
The landing gear of an aircraft is constituted of three gears that are a pair or a plurality of main landing gears set at a slightly rear side from a center in a longitudinal direction of a fuselage, and a nose landing gear provided in the vicinity of a front end portion of a fuselage. At a parking time, the main landing gears support approximately 90% of a fuselage weight, and the nose landing gear supports a remainder of about 10%. Since cargo compartments are provided at a front side and a rear side of the main landing gears, if the loading amount into the cargo compartment at the rear side becomes excessive, a so-called tailstrike accident occurs, in which the nose landing gear rises, and a fuselage rear portion touches the ground.
On the contrary, if the loading amount into the cargo compartment at the front side from the main landing gears becomes excessive, it leads to a so-called nose landing gear breakage accident, in which the nose landing gear that has the strength for only carrying about 10% of the fuselage weight as described above and is configured to be as light as possible is broken. Both a tailstrike accident and a nose landing gear breakage accident have to be absolutely avoided since an enormous trouble occurs to the subsequent operation, and enormous cost is required for repair of the fuselage.
Conventionally, in order to prevent a tailstrike accident of a fuselage, a support pole that is called a tail stanchion has been interposed between a tail portion of the fuselage and the ground to prevent the tail portion of the fuselage from lowering, and a measure called tethering that monitors the rising degree of a nose landing gear has been taken. Tethering is a method in which a rope is loosely extended from the ground to be laid on a nose landing gear, a specific observer monitors a degree of tension thereof, and if the front portion of the fuselage rises and the rope is stretched, the observer warns a luggage handler who performs loading and unloading of cargo.